Hi, I've enjoyed this forum as a lurker for the last year and this is my first post (although a veteran of many music boards). Thanks to everyone who's contributed to making this such an excellent and informative board!
On to the subject at hand...I've been fighting one problem in my control room, lack of 105hz-115hz (approx) in the listening position. The short term solution has been a subwoofer and checking my mixes standing in the "Club" (my nickname for the sides and back of the room where the bass really lives).
The room was built by the previous tenant and is floated, glass in front facing live room, double sheetrock walls with aluminum studs (I reinforced the sidewalls with a layer of 3/4"ply vertical, then oak slat wall horizontal on the side walls which tightened the low end).
The sidewalls are slightly angled, wider in the back so the dimensions are:
Height: 8'3"
Depth: 16'5" wall to wall, 16'8" wall to glass (the window is 3" inset)
Width: front 14'9", rear 15'8"
Plugging this into the Bob Gold room calculator doesn't look great -obviously the previous designers didn't do this, lol.
averaging things to: 16'6"d x 15'w x 8'3h the room is 1:1.84:2 which fails 2 of 3 tests.
I suspect my lack of the 110hz area is due to double cancellations.
If I extend the back wall by 12" things change dramatically:
17'6" x 15'w x 8'3h equals: 1: 1.83: 2.12 which passes all three tests and looks good according to the BBC spec.
So I have two questions:
Will a 1 foot change really translate in the real world to noticeably better bass response?
If so, what would be the ideal shape for the back wall -straight, angled....
A few more details: I will probably not move the entire rear wall. For structural reasons, it is much easier to cut out a 6'h x 10'w area and move that back 12 or 13". This wall can be straight (for maximum increase in volume) and filled with 703frk, or angled any direction (for less increase in dimension in volume).
I appreciate any thoughts on this.
Redo Back Wall? Slanted or Straight?
Originally posted at johnlsayers.com, topic 14877.
Yes. Who wrote anything about angling the rear wall? AndreWill a 1 foot change really translate in the real world to noticeably better bass response? If so, what would be the ideal shape for the back wall -straight, angled....
The height and the length of your room, length being divisible by the height, plugged into the calculator you used, produce:
110.1 hz 1.5% 10'3", 5'2", 2'7" (3,1,0 Tangential)
Do you have an overhead cloud at the mixing position? Do you have any bass trapping anywhere in this room?
Please see attachments for bass trapping.
The room is treated, however I strongly suspect that up until now I have been fighting the original design with trapping rather than addressing the design.
I dunno, your pix suggest that your listening position is jamb up into the right hand corner and that alone is enough to alter your symmetry...hard surfaces on the right hand side enough to reflect those higher frequencies back into at least the right side of your head.
Those amp heads alone [to the right hand side] might be enough to produce the noise you are supposedly having issue with.
That cloud broken up like it is, I would have to address that, what it is made of, why it angles and specifically what is it made of.
Andre knows this stuff inside and out so his opinion will be more important than what I have to say.
For what it's worth, I don't see a lot of bass trapping at all in that room. I would expect that it needs more than just the little bit that you show. You don't seem to have much trapping at all to speak of in the rear, for example.
I also agree with Brien, that there seem to be issues of symmetry and reflections.
But have you actually measured the response in that room? That would be the best starting point, I reckon. Measure the actual response at the mix position (especially in the low end), and see what the room is really doing at present.
- Stuart -
The listening position is in the middle of the room relative to the left/right walls so I'm not sure what's leading you to believe it's jammed into the right corner. The side walls are all lined with 2" and 4" of 703 in the front half of the room (extending beyond the listening position).I dunno, your pix suggest that your listening position is jamb up into the right hand corner and that alone is enough to alter your symmetry...hard surfaces on the right hand side enough to reflect those higher frequencies back into at least the right side of your head.
The amp heads do create some "shine" in the upper mids but for tracking I make the mental adjustment. It's a tradeoff for the functionality of having them there. When mixing I put a gobo in front of them (and over the front glass) which smooths out the mids and tightens the imaging. My concern is with the 100hz area, what makes you think the amps would have any effect on the 110hz frequency range?Those amp heads alone [to the right hand side] might be enough to produce the noise you are supposedly having issue with.
The "flying V" above my head is an idea I wanted to try. From the listening position we put mirrors on the walls and ceiling. At the point where I could see the speakers we created angled surfaces using double sheetrock with wood framing which we then put an absorbing layer of 2" 703. In addition to the V over my head we built two winged walls to the left and right of my listening position (about 2.5feet wide and floor to ceiling height). My thought behind this is that the high frequency first reflections get absorbed by the 2" fiberglass, and all the frequencies below that are also being bounced away by the underlying sheetrock. The conventional method of putting a gobo over a flat wall, and a soft ceiling clout over a flat ceiling are potentially allowing the lower mid frequencies to pass through and bounce to the listening position. On a flat wall, and flat ceiling, simply covering it with gobos only stops reflections down to the mids. That means that it is likely that a lot of side treatments are allowing those lower muddy frequencies (200hz-450hz) to pass through and bounce right to the listening position. To the degree that the upper lows are still directional around 150hz - 200hz those are very likely passing through soft treatments as well. I agree with the fact that the room could use more bass traps, but it's a bit of a chicken and egg situation. I don't want to go crazy trying to band-aide a design problem with treatments. I would rather make any structural changes now and then go crazy with traps once I have a solid foundation.That cloud broken up like it is, I would have to address that, what it is made of, why it angles and specifically what is it made of.
The picture you showed us is clear that there is a shorter area to the right hand side of the mix position...and that a door with all the air it takes to get to that opposing wall, exists, in spite of what you suggest.
Your overhead floor plan will bear this out as well.
As said earlier:
"The height and the length of your room, length being divisible by the height, plugged into the calculator you used, produce:
110.1 hz 1.5% 10'3", 5'2", 2'7" (3,1,0 Tangential)"
There in is your starting point.
What does the percentage, 1.5% mean? ThanksAs said earlier: "The height and the length of your room, length being divisible by the height, plugged into the calculator you used, produce: 110.1 hz 1.5% 10'3", 5'2", 2'7" (3,1,0 Tangential)" There in is your starting point.
Reading the updated Master handbook of Acoustics, Chapter 25, Acoustic Distortion (Peter D'Antonio):
"The next type of acoustic distortion is due to the coherent interference between the direct sound of a loud speaker and the reflections from the room, in particular the corner immediately surrounding it. This distortion occurs across the entire frequency spectrum but is more significant at low frequencies. It is called the speaker-boundary interference response."
It's a given that moving the speakers into corners enhances the low frequency, so we try hard to keep out of those corners unless it becomes part of the process/arrangement. And the monitor placement in an symmetrical room ensures some balance between the stereo image/frequency response.
And that can be effected by the sitting position, if the speakers are up against a wall, the head of the listener is in a peak or null area of the room and/or if some measure of attention has not been given to this placement.
You can build the trap, but I wonder out loud can this issue be improved by a better arrangement of the speakers/mixing position/more symmetry in mixing position?
Because I know how disruptive remodeling can be, if this were mine, I would look into all the elements of my positioning first.
The percentage point represents how far apart one frequency is from another.